Cleaning of photoconductive insulating surfaces

ABSTRACT

COMPOSITION FOR CLEANING PHOTOCONDUCTIVE INSULATING SURFACES COMPRISED OF AN AQUEOUS-ORGANIC LIQUID EMULSION, AND A SURFACTANT. THE COMPOSITION MAY FURTHER INCLUDE AN ABRASIVE AND SUSPENDING AGENT. THE COMPOSITION PREFERABLY INCLUDES A NON-FLAMMABLE ORGANIC LIQUID OF LOW TOXICITY; E.G., TETRACHLOROETHYLENE, WHICH IS EMULSIFIED IN THE WATER IN AN AMOUNT TO CONTROL THE VOLATILITY THEREOF AND THEREBY PROVIDE A COMPOSITIN WHICH EVAPORATES FROM THE SURFACE TO BE CLEANED AT A RATE THAT PERMITS EFFECTIVE CLEANING WITHOUT PRODUCNG SOLVENT FILMS OR STAINS.

United States Patent 3,702,303 CLEANING OF PHOTOCONDUCTIVE INSULATING SURFACES Carl F. Clemens and Thomas B. Baker, Webster, N.Y., assignors to Xerox Corporation, Stamford, Conn. No Drawing. Filed Sept. 15, 1970, Ser. No. 72,547 Int. Cl. C09d 9/62; Clld 7/50; C23g /02 U.S. Cl. 252-163 10 Claims ABSTRACT OF THE DISCLOSURE Composition for cleaning photoconductive insulating BACKGROUND OF THE INVENTION This invention relates to cleaning and/or pumicing compositions and more particularly to the cleaning and/or pumicing of a photoconductive insulating surface. Still more particularly, this invention relates to the cleaning and/or pumicing of a reusable electrophotographic plate or drum.

In the electrophotographic process, for example, as disclosed in Carlson Pat. No. 2,297,691, issued Oct. 6, 1942, an electrophotographic plate, comprising a photoconductive insulating material on a conductive backing, is given a uniform electric charge over its surface and is then exposed to the subject matter to be reproduced, usually by conventional projection techniques. This exposure discharges the plate areas in accordance with the light intensity which reaches them and thereby creates an electrostatic latent image on or in the plate coating.

Development of the electrostatic latent image is usually effected by an electrostatically attractable material, which is generally a thermoplastic resin in the form of finely divided particles usually in the size range from 3 to microns, commonly referred to as toner powder. In the development of the electrostatic latent image, the toner powder is brought into surface contact with the coating and is held thereon electrostatically in a pattern corresponding to the electrostatic latent image. The developed image is then transferred to a suitable support material, such as paper, and fused thereon to make a permanent image. In the transfer step substantially all of the resin material or toner is caused to adhere to the support material to form the images, thereon, but usually a very small percentage of the resin material or toner remains on the electrophotographic surface.

The small quantity of resin material or toner remaining on the electrophotographic surface will affect future operating steps of the process, and if left remaining thereon, has an accumulative effect in that additional residual toner particles adhere more readily to the surface in both image and non-image areas thereon. In automatic machines using rotary drums, continuous cleaning of such residual toner particles is effected with a rotating brush in peripheral contact with the surface of the electrophotographic surface which removes any residual resin material or toner adhering thereon. The brush in turn is cleaned by the use of a flicking bar in combination with a vacuum system whereby residual resin material or toner removed from the brush by the flicking bar is entrained in air and then subsequently separated from the air by a suitable filter.

The continuous cleaning of the photoconducting insulating surface, as hereinabove described, or any of the other methods currently employed in the art, does not completely remove the toner material from the photoconductive insulating surface and, therefore, repeated use of the photoconductive insulating surfaces causes a thin film of the toner material to be formed thereon, which adversely affects the reproduction process. The thin film of toner material is removed from the photoconductive insulating surface of commercial machines by effecting periodic cleaning with a solvent which is generally flammable. There have been numerous attempts to develop a non-flammable cleaner for removing residual toner film from a photoconductive insulating surface, but such attempts have generally been unsuccessful; mainly as a result of the cleaner staining or spotting the photosensitive insulting layer.

SUMMARY OF THE INVENTION Accordingly, an object of this invention is to provide for improved cleaning and/or pumicing of photoconductive insulating surfaces.

Another object of this invention is to provide a nonflammable cleaning and/or pumicing composition for cleaning photoconductive insulating surfaces, in particular, electrophotographic drums or plates.

These and other objects of this invention should be more readily apparent from the following detailed description thereof.

The objects of this invention are broadly accomplished by providing a composition comprised of an organic liquid-aqueous emulsion in which the relative proportions of the components are controlled to produce a volatility which avoids the formation of solvent films. The composition may also include an abradant and is particularly suitable for cleaning and/or pumicing the surface of a reusable electrophotographic sensitive member, such as vitrified selenium or its alloys.

DETAILED DESCRIPTION OF THE INVENTION The cleaning composition of the present invention is basically a three component composition comprised of an organic liquid, a surfactant and water with the organic liquid being emulsified in the Water. The composition generally comprises from about 10 parts to about 50 parts of the organic liquid and 1 part to about 10 parts of the surfactant, based upon parts of the three components, with the remainder being water and all parts being by weight. If the composition is to be employed for both cleaning and pumicing, the composition should include the organic liquid and surfactant, in the amounts hereinabove prescribed, and in addition include from about 5 parts to about 30 parts of an abrasive, based upon 100 parts of the four component composition, with the remainder being water and all parts by weight.

The organic liquid component of the composition may be comprised of one or more organic compounds which either dissolves the toner or preferentially attracts the toner film from the photoconductive insulating surface. In addition, the organic compound(s) should have the following properties: insoluble or only partially soluble in water; i.e., can be emulsified in water; chemically stable and/or inactive with respect to the photoconductive insulating member; and volatile; i.e., capable of vaporizing under the cleaning conditions, generally ambient conditions, to thereby eliminate the necessity of using special procedures for removing the organic liquid from the surface which has been cleaned. In general, the organic liquid has a vapor pressure, at 20 C., of from about 3 mm. to

about 70 mm. The organic compound(s) is also preferably non-flammable and non-toxic to reduce the overall hazards involved in using and storing the cleaning compositions.

-As representative examples of volatile organic compounds which are immiscible with water which may be used alone or in combination with each other as the organic liquid component of the cleaning composition, there may be mentioned: halogenated hydrocarbons, such as trichloroethylene, tetrachloroethylene, tetrafluoroethylene, methylene chloride, carbon tetrachloride, ethylene dichloride, monochlorobenzene, dichlorobenzene and the like; alkanols, such as pentanol and the like; chlorinated alkanols; such as trichloroethanol and the like; hydroxylated ethers, such as, methyl Cellosolve, ethyl Cellosolve; ketones, such as, methyl propyl ketone, diisobutyl ketone and the like; hydrocarbon esters, such as, ethyl acetate, isopropyl acetate, and the like; hydrocarbons, such as xylene, toluene, turpentine, various petroleum solvents, such as mineral spirits; carbonates, such as diethyl carbonate and the like. The preferred compounds are the chlorinated aliphatic hydrocarbons, with tetrachloroethylene being particularly preferred as a result of its non flammability, low toxicity and ready availability. These organic compounds and others, having the hereinabove noted properties, should be readily apparent to those skilled in the art and therefore the scope of the invention is not limited to the hereinabove specified representative compounds.

The emulsification of the solvent in Water reduces the flammability of the cleaning composition thereby avoiding one of the serious drawbacks of the cleaning compositions heretofore employed in the art. In addition, the use of water permits control of the overall volatility of the cleaning composition, thereby permitting the use of organic compound(s) which heretofore were considered as too volatile for use in a cleaning composition. The proportions of organic liquid and water are controlled to provide the desired rate of evaporation of the organic liquid from the surface being cleaned; i.e., the rate of evaporation is controlled to be rapid enough to prevent an organic liquid film from being retained on the surface being cleaned which would require special procedures to effect removal thereof, and yet not so rapid that the toner being removed from the surface being cleaned will be redeposited during the cleaning operation. In general, the relative portions of the organic liquid and Water components are controlled within the hereinabove described ranges to provide a composition which will evaporate from the surface to be cleaned in less than minutes, but not less than 2 minutes, and preferably within a time period from 3-5 minutes. The choice of the optimum proportions is deemed to be well within the scope of those skilled in the art from the teachings herein.

In addition to the hereinabove noted improved and desirable results achieved by the use of the three component cleaning composition of the present invention, a further advantage is achieved as a result of the hydrophilichydrophobic properties of the composition. Thus, the photoconductive insulating surface to be cleaned is generally covered with oxidation products thereof which have hydrophilic properties. Consequently, the cleaning composition of the present invention, as a result of its hydrophilic properties, attracts such oxidation products thereby further improving the overall cleaning of the photoconductive insulating surface.

Thee surfactant may be comprised of one or more anionic, cationic or non-ionic surfactants which do not adversely effect the electrical properties of the photoconductive insulating surface, with non-ionic surfactants generally being most suitable in that many cationic and anionic surfactants do have such an adverse effect. The non-ionic surfactant may be any one of the wide variety of nonionic surfactants generally known in the art and as representative examples of such non-ionic surfactants, there may be mentioned: condensation products of higher fatty alcohols with alkylene oxide, such as the reaction product of oleyl alcohol with 10 ethylene oxide units; condensation products of alkylphenols, with alkylene oxide, such as the reaction product of isooctylphenol with 12 ethylene oxide units; condensation products of higher fatty acid amides with 5, or more, ethylene oxide units; polyethylene glycol esters of long chain fatty acids, such as tetraethylene glycol monopalmitate, hexaethyleneglycol monolaurate, nonaethyleneglycol monostearate, nonaethyleneglycol dioleate, tridecaethyleneglycol monoarachidate, tricosaethylene glycol monobehenate, tricosaethyleneglycol dibehenate, ethylene oxide condensation products of polyhydric alcohol partial higher fatty acid esters, and their inner anhydrides (mannitol-anhydride, called Mannitan,

and sorbitolanhydride, called Sorbitan), such as glycerol monopalmitate reacted with 10 molecules of ethylene oxide, pentaerythritol monooleate reacted with l2 molecules of ethylene oxide, sorbitan monostearate reacted with 10 to 15 molecules of ethylene oxide, mannitan monopalmitate reacted with 10 to 15 molecules of ethylene oxide; long chain polyglycols in which one hydroxyl group is esterified with a higher fatty acid and the other hydroxyl group is esterified with a low molecular alcohol, such as methoxypolyethylene glycol 550 monostearate (550 meaning the average molecular weight of the polyglycol ether); long chain diols and the like. The selection of a suitable surfactant is well within the scope of those skilled in the art and, therefore, no further explanation in this respect is required for a full understanding of the invention.

The surfactant has a dual purpose in the composition in that the surfactant increases the stability of the composition; i.e., longer storage capabilities, and in addition facilitates cleaning of the photoconductive insulating surface by suspending the toner particles in the cleamng composition.

The abradant employed in the composition of the invention, it any, is insoluble in the composition and has a pumicing ability suflrciently great to pumice the photoconductive insulating material to a highly reflective finish. In the case of a reusable xerographic drum or plate, the photoconductive insulating surface is relatively soft and, therefore, an abradant of particularly small particle size should be employed, generally an average particles size of less than about 10 microns, preferably from about 0.1 micron to about 10 microns. The abradant powder may be employed in any of a wide variety of forms, but particularly good results are achieved with a powder having a generally irregular shape and a uniform particle size. As representative examples of suitable abradants, there may be mentioned: calcium phosphate, diatomaceous earth, alundum, carborundum, garnet, corundum, emery, iron oxide, chrome oxide, alumina, silica, celite, cerium oxide, calcium carbonate, tricalcium phosphite, bentonite, zirconium oxide, and the like.

The cleaning compositions which include an abradant generally also include an organic or inorganic suspending agent to improve the uniformity and stability of the composition. The suspending agent is generally employed in an amount from about 1 to about 6 parts, per parts of the five components of the composition, all parts being by weight, and as representative examples of such suspending agents, there may be mentioned, colloidal silica, kaolin, colloidal soot, zinc stearate, cadmium stearate and the like.

The cleaning composition of the invention may be produced by dissolving the non-ionic surfactant in the Water and subsequently emulsifying the organic solvent in the aqueous phase; for example, by Ultrasonics. The abrasive powder, if used, is then added to the emulsion and mixed thoroughly to provide a viscous liquid or paste-like product. It is to be understood, however, that the invention is not limited to any specific order of mixing the various components.

may be effected by impregnating a suitable medium which.

does not adversely affect the photoconductive insulating surface, such as gauze, paper toweling, absorbant cotton or a soft cloth, with the cleaning composition and rubbing the impregnated medium over the photoconductive insulating surface, preferably at a constant speed, for a period of time to effect the desired cleaning and/or pumicing. In using cleaning compositions which include an abrasive, the abradant must be removed from the cleaned and pumiced photoconductive insulating surface prior to its reuse. This may be easily effected by rubbing a water saturated pad over the photoconductive insulating surface followedby rubbing a dry absorbant pad over the surface.

The cleaning compositions of the present invention are particularly effective for cleaning and/ or pumicing a photoconductive insulating surface but it is to be understood that the compositions may also be employed for cleaning other surfaces; e.g., glass, and such other uses are included within the spirit and scope of the present invention.

The invention will be further described with reference to the following examples which are illustrative of preferred embodiments of the invention, but it is to be understood that the scope of the invention is not to be limited thereby. In the following examples, all parts and percentages are by weight.

EXAMPLES I-XI The following cleaning compositions are prepared by adding the surfactant to the water and emulsifying the organic liquid in the water by ultrasonics. The abrasive and suspending agent, if any, are added to the emulsion to provide a composition of paste-like consistency.

An amorphous selenium drum having a thin film of toner thereon, which is previously employed in an electrophotographic process in which a latent electrostatic image is developed thereon with a toner comprising a styrene-nbutyl methacrylate copolymer, polyvinyl butyral and carbon black produced as disclosed in Example I of US. Pat. No. 3,079,324 to Insalaco and the image subsequently transferred to a support, is cleaned with the following compositions by placing the composition on an absorbant pad and rubbing the pad over the surface of the drum with moderate pressure. Each of the compositions effectively removes the toner film without adversely effecting the electrical characteristics of the drum, and the compositions, including an abradant, pumice the drum to a highly reflective finish.

CLEANING COMPOSITIONS In the following examples, the surfactant employed is comprised of an equal mixture of Surfynol 82 and Igepon T- 1.

EXAMPLE V Parts Toluene Surfactant 2 Water 83 EXAMPLE VI Parts Petroleum solvent (sold under the mark Apcothinner) 15 Water 67 Surfactant 3 6 EXAMPLE VII Parts Turpentine 40 Surfactant 4 Water 56 EXAMPLE VIII Parts Mineral spirits 10 Trichloroethyl alcohol 30 Surfactant 10 Water 56 EXAMPLE IX Parts O-dichlorobenzene 10 Surfactant 2 Water 88 EXAMPLE X Parts Pentanol 20 Diisobutyl ketone 20 Surfactant 8 Water 52 EXAMPLE XI Parts Diethyl carbonate 50 Surfactant 5 Water 45 The cleaning compositions of the invention are particularly effective for removing the thin film formed on a reusable electrophotographic plate or drum, in particular a drum having an amorphous selenium surface, during repeated use thereof in that cleaning is effected without affecting the insulating or photoconducting properties of the surface and without leaving any stains or residues on the cleaned surface. The cleaning compositions of the present invention are particularly advantageous in that the preferred compositions are non-flammable and of low toxicity.

Numerous modifications and variations of the present invention are possible in light of the above teachings and, therefore, the invention may be practiced in a manner other than as particularly described.

What is claimed is:

1. A cleaning composition for cleaning photoconductive insulating surfaces consisting essentially of:

an emulsifiable volatile organic solvent, having a vapor pressure, at 20 C., of from about 3 mm. to about 70 mm., a surfactant selected from the group consisting of anionic, cationic and non-ionic surfactants which do not adversely effect the electrical properties of the photoconductive insulating surface and water, said volatile organic liquid being emulsified in said water, the organic liquid being present in an amount from about 10 parts to about 50 parts and the surfactant being present in an amount from about 1 part to about 10 parts, based upon parts of the three components, with the remainder being water and all parts by weight.

2. The composition of claim 1 wherein the surfactant is a non-ionic surfactant.

3. The composition of claim 2 wherein the organic solvent is tetrachloroethylene.

4. The composition of claim 2 wherein the composition further includes an insoluble abradant, said organic solvent being present in an amount from about 10 parts to about 50 parts, the surfactant being present in an amount from about 1 part to about 10 parts and said abradant being present in an amount from about 5 parts to about 30 parts, based upon 100 parts of the four components, with the remainder being water and all parts by weight.

5. The composition of claim 4 wherein the composition further includes a suspending agent for the abradant.

6. A process for cleaning a photoconductive insulating surface, comprising: rubbing the surface with a cleaning composition as defined in claim 1.

7. A process for cleaning a photoconductive insulating surface, comprising: rubbing the surface with a cleaning composition as defined in claim 2.

8. A process for cleaning a photoconductive insulating surface, comprising: rubbing the surface with a cleaning composition as defined in claim 3.

9. A process for cleaning a photoconductive insulating surface, comprising: rubbing the surface with a cleaning composition as defined in claim 4.

10. A process for cleaning a photoconductive insulating surface, comprising: rubbing the surface with a cleaning composition as defined in claim 5.

References Cited UNITED STATES PATENTS 3/1959 Mayer et al. 355-15 11/1914 Ellis 252-168 2/1936 Johnson 134-40 11/1959 Sohngen et al. 252-163 10/1966 Jones et a1. 252-163 7/1968 Riesberg 134-40 12/1968 Hoxie 252-168 US. Cl. X.-R.

wuss STATES PATENT owns CERHHCATE @l CQRRECTWN;

Patent No. 3 ,702 ,303 Dated November 7 I972 Inventor) Carl F. Clemens and Thomas B. Barker It is ce'rtified that error appears in {he above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, Line P, the name Bal e1: should read --Barker-"-.

Column 3 Line 66 the word Thee should read ----The-.

Signed and sealed this 10th day of July 19 73.

(SEAL) Attest: I

EDWARD M.FLETCHER.I Rene Tegtmeyer L Attesting Officer Acting Commlssloner of Patents FORM P0 1050 (10-69) USCOMM-DC 603764 5 Patent No. 3 702,303 Dated November 7 1972 Inventofls) Carl F. Clemens and Thomas B. Barker It iscertified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, Line l, the name *Baker should read --Bar*ker'-.

Column 3 Line 66 the word *"lhee should read -Ihe--.

Signed and sealed this 10th day of July 1973.

(SEAL) Attest:

EDWARD M.FLETCHER. Rene Tegtmeyer Y L Attesting Officer Acting commlssloner of Patents FORM PO-1050 (10-69) I uscoMM-Dc 60376-P89 

